Project Summary Sports-related concussions are a major public health problem in the US, affecting 1.6 to 3.8 million youth each year. These concussions can disrupt brain function and contribute to long- term severe health conditions. Current guidelines for early clinical management of sports-related concussions call for physical and cognitive rest. However, these guidelines are not strongly evidence-based. Furthermore, the optimal levels of physical and cognitive rest needed to promote recovery are unknown, precluding personalized rest plans for youth with different concussion characteristics. The aims of this study are to: 1) objectively measure the physical and cognitive rest among youth with sports-related concussions, 2) identify optimal levels of rest in relation to post-concussive symptoms (PCS) and functional impairments, and 3) examine the relationship between the levels of rest and PCS and functional impairments for high versus low risk concussions. Youth ages 11 to 17 years old (n = 110) from 18 schools (15 high schools and 3 middle schools) will be recruited and enrolled at the beginning of season through sign consent from parents and assent from youth. Following a confirmed concussion diagnosis, injury information and acute clinical presentation will be assessed at the time of injury as part of routine clinical care. Participating youth will be followed to assess concussion outcomes, including functional impairments, at three time points: within 48 hours of injury, and at day 7 and day 45 post- concussion. A parent/legal guardian of the concussed youth will also be asked to report his/her child?s post-concussion outcomes at the three time points. In addition, participating youth will be monitored on daily physical and cognitive rest and PCS, using two electronic devices (Actigraph and Narrative Clip) and daily survey in various lengths until acute symptoms resolve. Objective and real-time data on the type, duration, and intensity of physical and cognitive rest/activity, collected here for the first time, will fill critical knowledge gaps regarding the level of rest needed for optimal recovery from high- or low-risk concussions. This study will provide formative data to support a subsequent randomized controlled trial comparing the effect of different levels of rest/activity on concussion outcomes. More importantly, the results will have a significant impact on clinical practice by shaping standards of care and informing treatment decisions about optimal rest/activity for sports-related concussions among youth. 1